Spraying of concrete onto predefined erected sheet forms, such as inflatable hollow structures, is known. The forms can be made of thin, flexible sheets or foils, such as welded fabric (e.g. nylon or polyester), which, when inflated, take a predefined shape, such as a dome, a cylinder or combinations of these, for instance. In some solutions the sheet form is removed after the concrete has set. In other solutions the form will constitute a significant part of the end product. For many solutions, it is common to fix the form to a flat base in a sealed manner, in such a way that the form encompasses a sealed-off volume together with the base.
EP 0357151 describes a method of spraying synthetic foam and concrete onto the inside of an inflated form.
International patent application publication WO89/00102 describes the manufacturing of building structures by spraying a building material formulation onto a form. The form can be removed after setting of the building material.
US patent publication U.S. Pat. No. 4,372,733 describes an apparatus for applying concrete onto an erected mould. The apparatus is adapted to rotate about the mould and apply concrete in strips around the mould. Furthermore, the concrete applying apparatus is adapted to the specific shape of the mould, in order to follow the mould surface. A rather complex and costly amount of equipment is used to apply concrete on the outer surface of the form. If the mould or the final product is large, the concrete applying apparatus must be correspondingly large.
Swiss patent publication CH 665 612 describes a concrete tank. If such a tank were to be made large, for instance for storage of large amounts of liquid natural gas or other hydrocarbons offshore, it would be un-practical to make it on land and then move it to the sea. Such large-scale tanks should perhaps be made at the coast, avoiding road transportation.